Methods, Systems, and Computer-Readable Media for Providing Notification of a Power Failure

ABSTRACT

Methods, systems, and computer-readable media provide for notifying an optical line termination (OLT) of a power failure. According to embodiments, a method for notifying an OLT of a power failure is provided. According to the method, a notification of a power failure at an optical network termination (ONT) is received. In response to receiving the notification, power is retrieved from a dedicated power storage unit dedicated to providing power for the transmission of a dying gasp alarm. The dying gasp alarm is transmitted to the OLT utilizing at least a portion of the power from the dedicated power storage unit. The dying gasp alarm notifies the OLT of the power failure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to commonly assigned U.S. patentapplication Ser. No. ______, filed concurrently herewith, titled“METHODS, SYSTEMS, AND COMPUTER-READABLE MEDIA FOR DETERMINING PHYSICALLAYER FAILURES,” with attorney docket number 070266; and commonlyassigned U.S. patent application Ser. No. 11/753,758, titled “METHODS,SYSTEMS, AND COMPUTER-READABLE MEDIA FOR RANGING A DEVICE IN APOINT-TO-MULTIPOINT NETWORK,” each of which is hereby incorporatedherein by reference.

TECHNICAL FIELD

This application relates generally to the field of communicationsnetworks. More specifically, the disclosure provided herein relates tothe field of diagnosing fiber failures.

BACKGROUND

The rapid growth of the Internet and other networks has led toincreasing demand for higher speeds and higher bandwidth to support theefficient and reliable transmission of video, audio, images, text,multimedia, and other data. Fiber optics provides a means by which totransmit such data at high speeds, at a high bandwidth, and with minimaldata degradation. While a number of existing networks may utilize fiberoptic cables for at least a portion of the network, the connection tothe end user or customer has historically been established with morecost-effective copper cables, which typically transfer data at lowerspeeds, at a lower bandwidth, and with a higher risk of data loss thanwith fiber optic cables.

The deployment of fiber optics to homes, businesses, and other entitiesis known as fiber to the X (“FTTX”), in which the X may refer to, forexample, the curb, the building, the premise, or the home. FTTX may bedeployed using a point-to-multipoint configuration known as a passiveoptical network (“PON”). With a PON, data from an optical linetermination (“OLT”) is transmitted on single fiber and is shared, via anoptical splitter, among a plurality of optical network terminations(“ONTs”), optical network units (“ONUs”), multi-dwelling units (“MDUs”),or the like. A PON is termed “passive” because there are no activeelectronics between the OLT and the ONTs. The OLT broadcasts the samesignals, via the optical splitter, to all ONTs in the PON. The ONTs mayrestrict the signals provided to the end user, however. For example,while the OLT may broadcast a plurality of offered services, such asplain old telephone service (“POTS”), voice over Internet Protocol(“VOIP”), broadband, and Internet Protocol television (“IPTV”), to allthe ONTs, the ONTs may restrict their signal output to only thoseservices subscribed by the end user customers.

A number of failures may potentially occur in the connection between theOLT and the ONT. In a first example, a fiber between the OLT and theoptical splitter may be cut or otherwise rendered ineffective. In asecond example, a fiber between the optical splitter and one of the ONTsmay be cut or otherwise rendered ineffective. In a third example, theONT may experience a power failure. In a fourth example, the ONT mayexperience a software failure. In a fifth example, the ONT mayexperience a hardware failure.

When a failure in the connection between the OLT and ONT is firstdiscovered, for example, when a customer notifies a service providerthat the customer is not receiving subscribed services, the serviceprovider must determine the reason for the failure and dispatch anappropriate technician to an appropriate location. For example, whilethe service provider may utilize one technician to fix fiber cuts, theservice provider may utilize another technician to fix ONT softwarefailures. If an inappropriate technician is dispatched, resources, suchas time and money, may be wasted in dispatching a new technician.Additionally, if a technician is dispatched to an incorrect location oris unaware of the source of the failure, the technician may wasteresources locating the source of the failure. The resources wasted bythe technician may also affect the customer as the customer may notreceive subscribed services until the failure is remedied.

SUMMARY

Embodiments of the disclosure presented herein include methods, systems,and computer-readable media for detecting a failure in a passive opticalnetwork (PON). According to one aspect, a method for notifying anoptical line termination (OLT) of a power failure is provided. Accordingto the method, a notification of a power failure at an optical networktermination (ONT) is received. In response to receiving thenotification, power is retrieved from a dedicated power storage unitdedicated to providing power for transmitting a dying gasp alarm. Thedying gasp alarm is transmitted to the OLT utilizing at least a portionof the power from the dedicated power storage unit. The dying gasp alarmnotifies the OLT of the power failure.

According to another aspect, a system for notifying an optical linetermination (OLT) of a power failure is provided. The system includes amemory and a processor functionally coupled to the memory. The memorystores a program containing code for notifying the OLT of the powerfailure. The processor is responsive to computer-executable instructionscontained in the program and operative to receive a notification of apower failure at an optical network termination (ONT); in response toreceiving the notification, receive power from a dedicated power storageunit dedicated to providing power for transmitting a dying gasp alarm;and transmit the dying gasp alarm to the OLT utilizing at least aportion of the power from the dedicated power storage unit. The dyinggasp alarm notifies the OLT of the power failure.

According to yet another aspect, a computer-readable medium havinginstructions stored thereon for execution by a processor to perform amethod for notifying an optical line termination (OLT) of a powerfailure is provided. According to the method, a notification of a powerfailure at an optical network termination (ONT) is received. In responseto receiving the notification, power is retrieved from a dedicated powerstorage unit dedicated to providing power for transmitting a dying gaspalarm. The dying gasp alarm is transmitted to the OLT utilizing at leasta portion of the power from the dedicated power storage unit. The dyinggasp alarm notifies the OLT of the power failure.

Other systems, methods, and/or computer program products according toembodiments will be or become apparent to one with skill in the art uponreview of the following drawings and detailed description. It isintended that all such additional systems, methods, and/or computerprogram products be included within this description, be within thescope of the present invention, and be protected by the accompanyingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system configured to notify anoptical line termination (“OLT”) of a power failure, in accordance withexemplary embodiments.

FIG. 2 is a block diagram illustrating an OLT configured to determine alocation of a fiber cut, in accordance with exemplary embodiments.

FIG. 3 is a block diagram illustrating a passive optical network(“PON”), in accordance with exemplary embodiments.

FIG. 4 illustrates an exemplary optical time domain reflectometry(“OTDR”) trace.

FIG. 5 is a block diagram illustrating a power flow of an opticalnetwork termination (“ONT”), in accordance with exemplary embodiments.

FIG. 6 is a flow diagram illustrating a method for notifying the OLT ofa power failure, in accordance with exemplary embodiments.

FIG. 7 is a block diagram illustrating OTDR system, in accordance withexemplary embodiments.

FIG. 8 is a flow diagram illustrating a method for determining alocation of a fiber cut, in accordance with exemplary embodiments.

FIG. 9 is a flow diagram illustrating a method for generating a basesignature, according to exemplary embodiments.

DETAILED DESCRIPTION

The following detailed description is directed to methods, systems, andcomputer-readable media for notifying an optical line termination of apower failure. The following detailed description is further directed tomethods, systems, and computer-readable media for determining a locationof a fiber cut. In the following detailed description, references aremade to the accompanying drawings that form a part hereof, and which areshown by way of illustration specific embodiments or examples.

For the sake of simplicity and without limitation, the passive opticalnetworks (“PONs”) described in embodiments herein refer primarily tooptical network terminations (“ONTs”). However, it will be apparent tothose of ordinary skill in the art that the ONTs may be substituted withoptical network units (“ONUs”), multi-dwelling units (“MDUs”), or thelike. Additionally, it should be appreciated that the embodimentsdescribed herein may be applicable for any suitable FTTX deploymentincluding, but not limited to, fiber to the curb (“FTTC”), fiber to thebuilding (“FTTB”), fiber to the premise (“FTTP”), or fiber to the home(“FTTH”).

Referring now to the drawings, it is to be understood that like numeralsrepresent like elements through the several figures, and that not allcomponents and/or steps described and illustrated with reference to thefigures are required for all embodiments. FIG. 1 and the followingdiscussion are intended to provide a brief, general description of asuitable ONT in which embodiments may be implemented. FIG. 2 and thefollowing discussion are intended to provide a brief, generaldescription of a suitable optical network termination (“OLT”) in whichembodiments may be implemented. While embodiments will be described inthe general context of program modules that execute in conjunction withan application program that runs on an operating system on a computersystem, those skilled in the art will recognize that the embodiments mayalso be implemented in combination with other program modules.

Generally, program modules include routines, programs, components, datastructures, and other types of structures that perform particular tasksor implement particular abstract data types. Moreover, those skilled inthe art will appreciate that embodiments may be practiced with othercomputer system configurations, including hand-held devices,multiprocessor systems, microprocessor-based or programmable consumerelectronics, minicomputers, mainframe computers, and the like. Theembodiments may also be practiced in distributed computing environmentswhere tasks are performed by remote processing devices that are linkedthrough a communications network. In a distributed computingenvironment, program modules may be located in both local and remotememory storage devices.

FIG. 1 is a block diagram illustrating an optical network termination(“ONT”) 100 configured to notify an optical line termination (“OLT”),such as an OLT 200 of FIG. 2, of a power failure, in accordance withexemplary embodiments. The ONT 100 includes a processing unit 102, amemory 104, one or more user interface devices 106, one or moreinput/output (“I/O”) devices 108, and one or more network devices 110,each of which is operatively connected to a system bus 112. The bus 112enables bi-directional communication between the processing unit 102,the memory 104, the user interface devices 106, the I/O devices 108, andthe network devices 110. Although not shown in FIG. 1, the ONT 100 mayfurther include a physical layer loop back unit 322 as described ingreater detail below with respect to FIG. 3.

The processing unit 102 may be a standard central processor thatperforms arithmetic and logical operations, a more specific purposeprogrammable logic controller (“PLC”), a programmable gate array, orother type of processor known to those skilled in the art and suitablefor controlling the operation of the server computer. Processing unitsare well-known in the art, and therefore not described in further detailherein.

The memory 104 communicates with the processing unit 102 via the systembus 112. In one embodiment, the memory 104 is operatively connected to amemory controller (not shown) that enables communication with theprocessing unit 102 via the system bus 112. According to exemplaryembodiments, the memory 104 includes a dying gasp alarm module 116. Inone embodiment, the dying gasp alarm module 116 is embodied incomputer-readable media containing instructions that, when executed bythe processing unit 102, perform a method for notifying an OLT, such asthe OLT 200, of a power failure, as described in greater detail below.According to further embodiments, the dying gasp alarm module 116 may beembodied in hardware, software, firmware, or any combination thereof.

By way of example, and not limitation, computer-readable media maycomprise computer storage media and communication media. Computerstorage media includes volatile and non-volatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules, or other data. Computer storage media includes, but isnot limited to, RAM, ROM, Erasable Programmable ROM (“EPROM”),Electrically Erasable Programmable ROM (“EEPROM”), flash memory or othersolid state memory technology, CD-ROM, digital versatile disks (“DVD”),or other optical storage, magnetic cassettes, magnetic tape, magneticdisk storage or other magnetic storage devices, or any other mediumwhich can be used to store the desired information and which can beaccessed by the ONT 100.

The user interface devices 106 may include one or more devices withwhich a user accesses the ONT 100. The user interface devices 106 mayinclude, but is not limited to, computers, servers, personal digitalassistants, cellular phones, or any suitable computing devices.According to exemplary embodiments, the I/O devices 108 enable a user tointerface with the dying gasp alarm module 116. In one embodiment, theI/O devices 108 are operatively connected to an I/O controller (notshown) that enables communication with the processing unit 102 via thesystem bus 112. The I/O devices 108 may include one or more inputdevices, such as, but not limited to, a keyboard, a mouse, or anelectronic stylus. Further, the I/O devices 108 may include one or moreoutput devices, such as, but not limited to, a display screen or aprinter.

The one or more network devices 110 enable the ONT 100 to communicatewith other networks or remote systems via a network 120. Examples of thenetwork devices 110 may include, but are not limited to, a modem, aradio frequency (“RF”) or infrared (“IR”) transceiver, a telephonicinterface, a bridge, a router, or a network card. The network 120 mayinclude a wireless network such as, but not limited to, a Wireless LocalArea Network (“WLAN”) such as a WI-FI network, a Wireless Wide AreaNetwork (“WWAN”), a Wireless Personal Area Network (“WPAN”) such asBLUETOOTH, a Wireless Metropolitan Area Network (“WMAN”) such a WiMAXnetwork, or a cellular network. Alternatively, the network 120 may be awired network such as, but not limited to, a Wide Area Network (“WAN”)such as the Internet, a Local Area Network (“LAN”) such as the Ethernet,a wired Personal Area Network (“PAN”), or a wired Metropolitan AreaNetwork (“MAN”).

FIG. 2 is a block diagram illustrating the OLT 200 configured todetermine a location of a fiber cut, in accordance with exemplaryembodiments. The OLT 200 includes a processing unit 202, a memory 204,one or more user interface devices 206, one or more input/output (“I/O”)devices 208, and one or more network devices 210, each of which isoperatively connected to a system bus 212. The operations of theprocessing unit 202, the memory 204, the user interface devices 206, theI/O devices 208, the network devices 210, and the system bus 212 aresimilar to the processing unit 102, the user interface devices 106, theI/O devices 108, the network devices 110, and the system bus 112 of theONT 100. The network 220 may or may not be the same as the network 120.

The memory 204 includes a fiber cut determination module 216. In oneembodiment, the fiber cut determination module 216 is embodied incomputer-readable media containing instructions that, when executed bythe processing unit 202, perform a method for determining a location ofa fiber cut, as described in greater detail below. According to furtherembodiments, the fiber cut determination module 216 may be embodied inhardware, software, firmware, or any combination thereof.

FIG. 3 is a block diagram illustrating a passive optical network (“PON”)300, in accordance with exemplary embodiments. The PON 300 includes theoptical line termination (“OLT”) 200 coupled to a plurality of ONTs 100a-100 n (collectively ONTs 100) via an optical splitter 304. The OLT 200is further coupled to an element management system (“EMS”) 308 via anetwork 310. The network 310 may include a wireless network such as, butnot limited to, a WLAN such as a WI-FI network, a WWAN, a WPAN such asBLUETOOTH, a WMAN such a WiMAX network, or a cellular network.Alternatively, the network 310 may be a wired network such as, but notlimited to, a WAN such as the Internet, a LAN such as the Ethernet, awired PAN, or a wired MAN. The PON 300 includes any suitable number ofONTs, according to exemplary embodiments. For example, a BroadbandPassive Optical Network (“BPON”) standard may support up to thirty-twoONTs, and a Gigabit Passive Optical Network (“GPON”) standard maysupport up to sixty-four ONTs. In further embodiments, the PON 300 mayinclude two or more optical splitters 304.

Data transmissions between the OLT 200 and ONTs 100 may be achievedusing any suitable transmission standard including, but not limited to,BPON, GPON, Asynchronous Transfer Mode Passive Optical Network (“APON”),or Ethernet Passive Optical Network (“EPON”). A transmission from theOLT 200 to the ONTs 100 is referred herein as a “downstreamtransmission.” A transmission from the ONTs 100 to the OLT 200 isreferred herein as an “upstream transmission.” The OLT 200 is located ata service provider's central office (“CO”), and each ONT 100 is locatedat or near the customer's home, business, or other entity, according toexemplary embodiments.

For downstream transmissions, the service provider at the OLT 200 maybroadcast offered services 314 or other data through a fiber 316 tocustomers at all the ONTs 100. The offered services 314 are embodied inone or more optical signals utilizing one or more optical wavelengths,according to exemplary embodiments. The optical splitter 304 “passively”replicates the offered services 314 from the OLT 200 and transmits thereplicated services 314 a-314 n through fibers 318 a-318 n (collectivelyfibers 318) to the ONTs 100. When the ONTs 100 receive the replicatedservices 314 a-314 n from the optical splitter 304, the ONTs 100 mayrestrict the replicated services 314 a-314 n to only subscribed services320 a-320 n (collectively subscribed services 320) according to, forexample, individual customer information associated with each respectiveONT 100. The customer information may include, but is not limited to,the customer's name, address, and list of subscribed services. Thesubscribed services 320 are embodied in a plurality of electricalsignals, according to exemplary embodiments. In such embodiments, theONTs 100 may convert received optical signals to the electrical signals.

For upstream transmissions, the ONTs 100 may transmit data to the OLT200 at different time slots allocated by the OLT 200 for each ONT 100.The allocated time slots may be managed using any suitable accessprotocol including, but not limited to, the time division multipleaccess (“TDMA”) protocol. In one embodiment, the ONTs 100 convert dataembodied in one or more electrical signals into one or more opticalsignals prior to transmission to the OLT 200.

As illustrated in FIG. 3, the ONTs 100 each include the dying gasp alarmmodule 116 of FIG. 1, according to exemplary embodiments. The ONTs 100may each further include a capacitor or other dedicated power source,such as a dedicated power storage unit 406 of FIG. 5. The sole purposeof the dedicated power storage unit 406 is to provide an ONT, such asthe ONT 100 a, enough power to notify the OLT 200 of a power failure atthe ONT 100 a, according to exemplary embodiments.

As described in greater detail below with regards to FIGS. 4 and 5, theONTs 100 are each configured for receiving power from ONT power sources,such as commercial power and/or battery power, according to exemplaryembodiments. To distinguish power failures of the ONTs 100 from otherfailures, such as a fiber cut, the ONTs 100 may be configured totransmit a dying gasp alarm to the OLT 200. As used herein, the dyinggasp alarm refers to a notification from an ONT, such as the ONT 100 a,to the OLT 200 of a power failure at the ONT 100 a. However, during apower failure, the ONT 100 a may not have sufficient power to send thedying gasp alarm to the OLT 200. The dedicated power storage unit 406may provide the ONT 100 a at least enough power to transmit the dyinggasp alarm to the OLT 200 even if the ONT power sources are unavailable.Further, as previously described, the ONT 100 a is typically allocated aparticular time slot during which the ONT 100 a can communicate with theOLT 200. In one embodiment, the dying gasp alarm module 116 provides anappropriate protocol by which the ONT 100 a can timely transmit thedying gasp alarm to the OLT 200.

The ONTs 100 each further includes a physical layer loop back unit 322.The OLT 200 includes the fiber cut determination module 216, inaccordance with exemplary embodiments. The fiber cut determinationmodule 216 and the physical layer loop back unit 322 may be utilized inconjunction to determine a location of a fiber cut. In exemplaryembodiments, the physical layer loop back unit 322 providesfunctionality to the ONTs 100 whereby light transmitted to an ONT, suchas the ONT 100 a, may be reflected back to the OLT 200.

In exemplary embodiments, the fiber cut determination module 216provides the OLT 200 with optical time domain reflectometry (“OTDR”)functionality, thereby enabling the OLT 200 to transmit one or moreoptical test pulses across the fibers 318 to the ONT 100 a. In responseto the fiber cut determination module 216 transmitting the optical testpulses across the fibers 318, the fiber cut determination module 216receives reflected and back-scattered light resulting from the ONTs 100.In one embodiment, at least a portion of the reflected light is causedlight reflected back by the physical layer loop back unit 322 in the ONT100 a. The intensity and the arrival time of the pulses reflected backto the OLT 200 by the physical layer loop back unit 322 of the ONT 100 aare measured and plotted as a function of the lengths of the fibers 318,according to exemplary embodiments. This plot, also known as an OTDRtrace, is referred to herein as a signature. An exemplary OTDR trace 450is illustrated in FIG. 4. The OTDR trace 350 shows a location 356 of theOLT 200, a location 352 of the optical splitter 304, and a location 354of the ONTs 100. As shown in FIG. 4, the plurality of ONTs 100 areindistinguishable in the conventional OTDR trace 350.

Prior to an actual fiber cut, the fiber cut determination module 216 inthe OLT 200 is executed to generate a plurality of base signaturescorresponding to a plurality of configurations of working andnon-working ONTs 100, according to exemplary embodiments. As usedherein, a base signature refers to an OTDR trace with a knownconfiguration of working and non-working ONTs 100. A working ONT is onethat is configured to properly communicate with the OLT 200 and isrepresentative of an ONT not associated with a fiber cut. A non-workingONT is one that is configured to not properly communicate with the OLT200, effectively simulating a fiber cut between the non-working ONT andthe OLT 200. In one embodiment, an ONT, such as the ONT 100 a, isconfigured to properly communicate with the OLT 200 by enabling thephysical layer loop back unit 322 at the ONT 100 a. Similarly, the ONT100 a may be configured to not properly communicate with the OLT 200 bydisabling the physical layer loop back unit 322 at the ONT 100 a.

As previously described, the physical layer loop back unit 322 providesfunctionality to the ONT 100 a whereby light transmitted by the OLT 200to the ONT 100 a may be reflected back to the OLT 200. Because the basesignature is generated based, at least in part, on the light reflectedback from the physical layer loop back unit 322, each base signaturewill likely differ depending on whether the various physical layer loopback units 322 at the ONTs 100 are enabled or disabled. By enabling ordisabling the physical layer loop back units 322 at the ONTs 100, fibercuts between the OLT 200 and the ONTs 100 can be effectively simulatedto generate the plurality of base signatures corresponding to aplurality of configurations of working and non-working ONTs.

In one embodiment, the fiber cut determination module 216 is executed togenerate a base signature corresponding to every possible combination ofworking and non-working ONTs 100 in the PON 300. For example, if the PON300 includes the first ONT 100 a, the ONT 100 b, and the ONT 100 n, thefiber cut determination module 216 may be executed to generate eightbase signatures: (1) ONTs 100 a-100 n are all working; (2) ONTs 100 aand 100 b are working and ONT 100 n is not working; (3) ONTs 100 a and100 n are working and ONT 100 b is not working; (4) ONTs 100 b and 100 nare working and ONT 100 a is not working; (5) ONT 100 a is working andONTs 100 b and 100 n are not working; (6) ONT 100 b is working and ONTs100 a and 100 n are not working; (7) ONT 100 n is working and ONTs 100 aand 100 b are not working; and (8) ONTs 100 a-100 n are all not working.In one embodiment, the number of base signatures that need to begenerated is relative to the number of ONTs 100 in the PON 300. Itshould be appreciated that any number of base signatures may begenerated to be used to determine the location of a fiber cut.

After determining or suspecting that a fiber cut has occurred, the fibercut determination module 216 in the OLT 200 is executed to generate acurrent signature reflecting the current state of the PON 300, accordingto exemplary embodiments. Similar to generating the base signatures, thecurrent signature is also generated by transmitting optical test pulsesfrom the OLT 200 to each of the ONTs 100. During the generation of thecurrent signature, each of the ONTs 100 enables the physical layer loopback unit 322. If an ONT does not have a fiber cut, then the physicallayer loop back unit 322 will reflect the optical test pulses back tothe OLT 200. However, if an ONT does have a fiber cut, then the opticaltest pulses will not reach the ONT and the optical test pulses will notbe reflected back to the OLT 200 even though physical layer loop backunit 322 is enabled. After generating the current signature, the fibercut determination module 216 compares the current signature to theplurality of base signatures to find a base signature matching thecurrent signature. If a matching base signature is found, then thematching base signature may be used to determine which of the fibers 318is/are cut because the base signature was generated under a knownconfiguration of working and non-working ONTs.

FIG. 5 is a block diagram illustrating a power flow 400 of an ONT, suchas the ONT 100 a, in accordance with exemplary embodiments. The ONT 100a includes one or more plain old telephone service (“POTS”) ports 402and one or more Ethernet ports 404, according to one embodiment. Infurther embodiments, the ONT 100 a may include any suitable ports, suchas craft ports, or other physical interfaces. The ONT 100 a furtherincludes the dying gasp alarm module 116 of FIG. 1. The dying gasp alarmmodule 116 includes the dedicated power storage unit 406 and a transferprotocol module 408, according to exemplary embodiments. The power flow400 further includes a power supply 410 for receiving commercial powerfrom an electric company, for example. The power supply 410 includes abattery backup 412, according to one embodiment. The power supply 410may further include an alternating current/direct current (“AC/DC”)converter and charging circuitry (not shown) for charging the batterybackup 412. In further embodiments, the ONT 100 a receives power fromany suitable power sources.

According to exemplary embodiments, the ONT 100 a is powered bycommercial power received through the power supply 410. If the powersupply 410 ceases to receive commercial power, the power supply 410reverts to the battery backup 412. The power supply 410 may cease toreceive commercial power for any number of reasons including, but notlimited to, a power outage or a cut electrical cable. In one embodiment,when the battery backup 412 falls below a given voltage, the ONT 100 atransmits a dying gasp alarm to the OLT 200 to signal to the OLT 200 apower failure at the ONT 100 a. However, the dying gasp alarm may notreach the OLT 200 for any number of reasons including, but not limitedto, high traffic on the ONT 100 a such that the dying gasp alarm is notretrieved before the battery backup 312 dies or heavy load on the ONT100 a such that the battery backup 412 is so heavily utilized thatinsufficient power is available to transmit the dying gasp alarm.

The dedicated power storage unit 406 may be a capacitor or any othersuitable power storage device. The dedicated power storage unit 406 isreferred to as “dedicated” because the sole purpose of the dedicatedpower storage unit 406, unlike the battery backup 412, is to providepower for the transfer protocol module 408 to transmit a dying gaspalarm to the OLT 200, according to exemplary embodiments. Therefore,even if the battery backup 412 fails before a dying gasp alarm isretrieved from the ONT 100 a, the dedicated power storage unit 406provides power to the transfer protocol module 408 such that the dyinggas alarm can be transmitted, according to exemplary embodiments. Inparticular, the dedicated power storage unit 406 may be independent ofthe operations of the ONT 100 a apart from transmitting the dying gaspalarm. In one embodiment, the dedicated power storage unit 406 is notutilized by the transfer protocol module 408 until the battery backup412 dies or is about to die as indicated by, for example, the voltage ofthe battery backup 412. In one embodiment, the power supply 410, thebattery backup 412, and the dedicated power storage unit 406 areconfigured in a series circuit.

In one embodiment, the transfer protocol module 408 provides one or moreprotocols for transmitting a dying gasp alarm from the ONT 100 a to theOLT 200. Prior to transmitting the dying gasp alarm, the ONT 100 a maydisable one or more unnecessary power-consuming devices and drivers,such as the POTS port 402, the Ethernet port 404, a dial-tone generator(not shown), and the like. In one embodiment, the transfer protocolmodule 408 transmits the dying gasp alarm from the ONT 100 a to the OLT200 via a Physical Layer Operations and Maintenance (“PLOAM”) message asspecified under the International Telecommunications Union (“ITU”)G983.1 standard. With PLOAM, which is a poll-based messaging protocol,the ONT 100 a places the dying gasp alarm or other message in anupstream queue. The OLT 200 traverses the upstream queue of each of theONTs 100 at given intervals and retrieves messages from the upstreamqueue. The ITU G983.1 standard defines the minimum PLOAM rate per ONT asone PLOAM cell every 100 ms. In one embodiment, the dedicated powerstorage unit 406 provides the transfer protocol module 408 at least 100ms of operation time or enough operation time to transmit a PLOAMmessage. PLOAM messages provide a dedicated queue, a fixed size, andassociated priority defined in ITU 983.1.

In further embodiments, the transfer protocol module 408 transmits thedying gasp alarm from the ONT 100 a to the OLT 200 via an OpticalNetwork Termination Management and Control Interface (“OMCI”) message asspecified under the ITU G983.1 standard. With OMCI, the dying gasp alarmmay be treated with higher priority for upstream transmission. If theupstream queues from the ONTs 100 to the OLT 200 are designedappropriately to establish the highest priority for the queue containingthe dying gasp alarm, the transmission of the dying gasp alarm may bereduced to about 50 ms. In one embodiment, the dedicated power storageunit 406 provides the transfer protocol module 408 at least 50 ms ofoperation time or enough operation time to transmit an OMCI message.Similar to the PLOAM messages described above, OMCI messages are queuedinto an OMCI queue. The OMCI queue has an associated priority comparedto the traffic related queues, such as control traffic (e.g., InternetGroup Management Protocol (“IGMP”), Session Initiation Protocol(“SIP”)), constant bit rate traffic, variable bit rate traffic realtime, variable bit rate non real time, best effort traffic, and thelike. Each queue may be administrable based on the services provided andmay be designed in terms of a size and a priority. If a queue is notdeep enough (i.e., short), then messages will be lost. If the controltraffic queue is a low priority, then subscribers will have issuesjoining a multicast stream via IGMP or making a phone call via SIP.

In further embodiments, the transfer protocol module 408 may send thedying gasp alarm multiple times utilizing multiple transmissionprotocols, such as PLOAM and OMCI, to ensure that the dying gasp alarmreaches the OLT 200. In further embodiments, the dedicated power storageunit 406 provides the transfer protocol module 408 at least enoughoperation time to transmit the dying gasp alarm from the ONTs 100 to theOLT 200 under any suitable transmission protocol.

FIG. 6 is a flow diagram illustrating a method 500 for notifying the OLT200 of a power failure, in accordance with exemplary embodiments.Referring to FIGS. 3, 4, and 5, the transfer protocol module 408receives (at 502) notification that an ONT, such as the ONT 100 a,experienced a power failure. A power failure may include, but is notlimited to, a power outage, a cut electrical cable, a defective powersupply 410, or a dead or near-dead battery backup 412. In response toreceiving notification of the power failure, the transfer protocolmodule 408 terminates (at 504) unnecessary power-consuming drivers anddevices, such as the POTS port 402, the Ethernet port 404, a dial-tonegenerator, or the like, in the ONT 100 a. Further, in response toreceiving notification of the power failure, the transfer protocolmodule 408 receives (at 506) power from the dedicated power storage unit406. While receiving power from the dedicated power storage unit 406,the transfer protocol module 408 transmits (at 508) a dying gasp alarmto the OLT 200. As previously described, the sole purpose of thededicated power storage unit 406 is to provide the ONT 100 a sufficientpower for which to transmit the dying gasp alarm during a power failure,according to exemplary embodiments. The dying gasp alarm notifies theOLT 200 of the power failure at the ONT 100 a. The dying gasp alarm maybe transmitted under any suitable transmission protocol including, butnot limited to, PLOAM or OMCI.

FIG. 7 is a block diagram illustrating an OTDR system 600, in accordancewith exemplary embodiments. The OTDR system 600 includes the OLT 200 andthe ONTs 100 a and 100 b coupled to the OLT 200 via the fibers 318 a and318 b, respectively. As illustrated in FIG. 7, the fiber 318 a includesa fiber cut 602 while the fiber 318 b does not include any fiber cut.According to exemplary embodiments, prior to the fiber cut 602, thefiber cut determination module 216 generates a plurality of basesignatures by transmitting optical test pulses 604 across the fibers 318a and 318 b. The fiber cut determination 216 generates at least fourbase signatures, according to one embodiment: (1) a first base signaturecorresponding to no fiber cuts on both the fibers 318 a and 318 b; l (2)a second base signature corresponding to a fiber cut on the fiber 318 abut no fiber cut on fiber 318 b; (3) a third base signaturecorresponding to a fiber cut on fiber 318 b but no fiber cut on fiber318 a; and (4) a fourth base signature corresponding to fiber cuts onboth fibers 318 a and 318 b. As previously described, a fiber cut at anONT, such as the ONT 100 a, may be simulated during the generation ofthe base signatures by disabling the physical layer loop back unit 322of the ONT 100. By enabling or disabling the physical layer loop backunits 322, different base signatures may be generated because an enabledphysical layer loop back unit will reflect light while a disabledphysical layer loop back unit will not reflect light.

In response to transmitting the optical test pulses 604 across thefibers 318 a and 318 b, the fiber cut determination module 216 measuresthe intensity and the arrival time of back-scattered light 606 andreflected light 608 resulting from the transmission of the optical testpulses 604. The back-scattered light may be caused by, for example,Rayleigh scattering, and the reflected light may caused by, for example,Fresnel reflection. The measured intensity and arrival time of theback-scattered light 606 and the reflected light 608 for the ONTs 100 aand 100 b may then be plotted as a function of the lengths of the fibers318 a and 318 b, respectively, to generate the plurality of basesignatures. The OTDR trace may reflect the difference between fibers ofdifferent lengths based on arrival time of the reflected time.

After the fiber cut 602 occurs, it may be unknown whether the fiber cut602 is present in the fiber 318 a or the fiber 318 b. To determine thelocation of the fiber cut 602, the fiber cut determination module 216may generate a current signature by transmitting optical test pulses 604across the fibers 318 a and 318 b. During the generation of the currentsignature, the ONTs 100 a and 100 b each enables its correspondingphysical layer loop back unit 322. When the optical test pulses 604 aretransmitted across the fiber 318 b to the ONT 100 b, the physical layerloop back unit 322 associated with the ONT 100 b will reflect back theoptical test pulses 604 to the OLT 200 because the fiber 318 b includesno fiber cuts. However, when the optical test pulses 604 are transmittedacross the fiber 318 a to the ONT 100 a, the optical test pulses 604will not reach the ONT 100 a because the fiber 318 a includes the fibercut 602. As such, the physical layer loop back unit 322 associated withthe ONT 100 a will not reflect back the optical test pulses 604 to theOLT 200.

In response to transmitting the optical test pulses 604 across thefibers 318 a and 318 b, the fiber cut determination module 216 measuresthe intensity and the arrival time of the back-scattered light 606 andthe reflected light 608. The measured intensity and arrival time of theback-scattered light 606 and the reflected light 608 may then be plottedas a function of the lengths of the fibers 318 a and 318 b to generatethe current signature. Because the base signatures were generated bysimulating fiber cuts, comparing the current signature with the basesignatures may yield the location of the fiber cut 602 if a basesignature matching the current signature is found. If the location ofthe fiber cut 602 is found to be on the fiber 318 a, then an appropriatetechnician can be dispatched to the fiber 318 a without wasting timeconsidering whether the fiber cut 602 is also located in fiber 318 b.

The OTDR system 600 as described above with respect to FIG. 7 provides ameans to determine which of a plurality of fibers emanating from anoptical splitter, such as the optical splitter 304, contains a fibercut, according to exemplary embodiments. While traditional OTDR systemsand methods may indicate that a fiber cut exists somewhere in the PON,these systems and methods are generally unable to distinguish betweenone fiber at one ONT and other fibers at other ONTs, as previouslyillustrated in the OTDR trace 350 of FIG. 4. As such, a technicianutilizing these traditional OTDR systems and methods may need toconsider all the fibers at all the ONTs in the PON, thereby potentiallywasting considerable time, money, and effort.

FIG. 8 is a flow diagram illustrating a method 700 for determining alocation of a fiber cut, in accordance with exemplary embodiments. Priorto any fiber cut, the OLT 200 generates (at 702) a plurality of basesignatures. In exemplary embodiments, each of the base signaturesgenerated by the OLT 200 corresponds to a known configuration of workingONTs and non-working ONTs in the PON 300. A working ONT effectivelysimulates an ONT with no fiber cut by enabling the physical layer loopback unit 322. A non-working ONT effectively simulates an ONT with afiber cut by disabling the physical layer loop back unit 322. In oneembodiment, the number of base signatures generated is relative to thenumber of possible configurations of working and non-working ONTs in thePON 300. For example, the number of base signatures generated may be atleast equal to the number of possible configurations of working andnon-working ONTs.

Turning now to FIG. 9, a flow diagram illustrating a method 800 forgenerating a base signature is shown, according to exemplaryembodiments. The fiber cut determination module 216 of the OLT 200configures (at 802) each of the plurality of ONTs 100 in the PON 300 tocorrespond to a working ONT or a non-working ONT. An ONT, such as theONT 100 a, may be configured to correspond to a working ONT by enablingthe physical layer loop back unit 322 of the ONT 100 a. Alternatively,the ONT 100 a may be configured to correspond to a non-working ONT bydisabling the physical layer loop back unit 322 of the ONT 100 a. Inresponse to configuring the plurality of ONTs 100, the fiber cutdetermination module 216 transmits (at 804) one or more optical testpulses across each of the fibers 318. In response to transmitting theone or more optical test pulses, the fiber cut determination module 216receives (at 806) back-scattered light 606 and reflected light 608 fromthe fibers 318. The fiber cut determination module 216 measures (at 808)the intensity and the arrival time of the back-scattered light 606 andthe reflected light 608, and generates (at 810) a base signature byplotting the measured intensity and the arrival time of theback-scattered light 606 and the reflected light 608 as a function ofthe lengths of the fibers 318. The base signature may be stored in thememory 204, according to one embodiment. As an additional backuplocation in the event the memory 204 in the OLT 200 becomes lost orcorrupt, the base signature may also be sent to and stored in the EMS308. For example, if the OLT 200 loses data after an upgrade or aswapping of control cards, then the EMS 308 can provide a backup copy.Further, by storing the base signature in the EMS 308, then the basesignature can be pushed from the EMS 308 to multiple OLTs.

Referring again to FIG. 8, after a fiber cut, such as the fiber cut 602,is determined or suspected to exist in at least one of the fibers 318,the fiber cut determination module 216 generates (at 704) a currentsignature. The current signature is generated in a similar manner as thebase signature, as described with respect to FIG. 9, except that theONTs 100 are not pre-configured to correspond to a working or anon-working ONT. Instead, the physical layer loop back unit 322 of eachof the ONTs 100 is enabled. The current signature, therefore, reflectsthe current state of the ONTs 100 in the PON 300.

The fiber cut determination module 216 compares (at 706) the currentsignature with the plurality of base signatures to determine whether abase signature matching the current signature exists. If a matching basesignature is found, then the fiber cut determination module 216determines (at 708) the location of the fiber cut 602 based on the knownconfiguration of working and non-working ONTs used to generate thematching signature. Given the location of the fiber cut 602, anappropriate technician can be dispatched to the location of the fibercut 602 to fix the fiber cut 602.

Embodiments described and illustrated with reference to the Figuresprovide methods, systems, and computer-readable media for notifying anOLT of a power failure. In exemplary embodiments, the dedicated powerstorage unit 406 is provided to power the transfer protocol module 408.The transfer protocol module 408 is configured to transmit a dying gaspalarm from an ONT, such as ONT 100 a, to the OLT 200. The dying gaspalarm indicates that the ONT 100 a has suffered a power failure, asopposed to another failure, such as a fiber cut. The dedicated powerstorage unit 406 provides sufficient power such that the transferprotocol module 408 is able to successfully transmit the dying gaspalarm to the OLT 200 even if, for example, the battery backup 312 iscompletely dead.

Embodiments described and illustrated with reference to the Figuresfurther provide methods, systems, and computer-readable media fordetermining location of a fiber cut. In exemplary embodiments, the OLT200 includes the fiber cut determination module 216, which provides,among other things, OTDR functionality. The fiber cut determinationmodule 216 is further able to generate a plurality of base signaturesprior to a fiber cut and a current signature after a fiber cut. The basesignatures are generated based on known configurations of working andnon-working ONTs. The current signature reflects the current state ofthe ONTs 100 in the PON 300. By comparing the current signature with thebase signatures, the location of the fiber cut may be determined if thecurrent signature matches one of the base signatures.

Although the subject matter presented herein has been described inconjunction with one or more particular embodiments and implementations,it is to be understood that the embodiments defined in the appendedclaims are not necessarily limited to the specific structure,configuration, or functionality described herein. Rather, the specificstructure, configuration, and functionality are disclosed as exampleforms of implementing the claims.

The subject matter described above is provided by way of illustrationonly and should not be construed as limiting. Various modifications andchanges may be made to the subject matter described herein withoutfollowing the example embodiments and applications illustrated anddescribed, and without departing from the true spirit and scope of theembodiments, which is set forth in the following claims.

1. A method for notifying an optical line termination (OLT) of a powerfailure, comprising: receiving a notification of a power failure at anoptical network termination (ONT); in response to receiving thenotification, receiving power from a dedicated power storage unitdedicated to providing power for transmitting a dying gasp alarm; andtransmitting the dying gasp alarm to the OLT utilizing at least aportion of the power from the dedicated power storage unit, the dyinggasp alarm notifying the OLT of the power failure.
 2. The method ofclaim 1, further comprising: in response to receiving the notification,terminating at least one power-consuming device or driver.
 3. The methodof claim 1, wherein the dedicated power storage unit comprises acapacitor.
 4. The method of claim 1, wherein the dying gasp alarm istransmitted to the OLT via a Physical Layer Operations and Maintenance(PLOAM) message.
 5. The method of claim 1, wherein the dying gasp alarmis transmitted to the OLT via an Optical Network Termination Managementand Control Interface (OMCI) message.
 6. The method of claim 1, whereinthe power failure comprises at least one of a power outage, a cutelectrical cable, a defective power supply, and a dead or near deadbackup battery.
 7. The method of claim 1, wherein the notification istransmitted when a backup battery reaches a given voltage.
 8. A systemfor notifying an optical line termination (OLT) of a power failure,comprising: a memory for storing a program containing code for notifyingOLT of the power failure, comprising; a processor functionally coupledto the memory, the processor being responsive to computer-executableinstructions contained in the program and operative to: receive anotification of a power failure at an optical network termination (ONT);in response to receiving the notification, receive power from adedicated power storage unit dedicated to providing power fortransmitting a dying gasp alarm; and transmit the dying gasp alarm tothe OLT utilizing at least a portion of the power from the dedicatedpower storage unit, the dying gasp alarm notifying the OLT of the powerfailure.
 9. The system of claim 8, wherein the processor is responsiveto further computer-executable instructions contained in the program andoperative to: in response to receiving the notification, terminate apower-consuming device or driver.
 10. The system of claim 8, wherein thededicated power storage unit comprises a capacitor.
 11. The system ofclaim 8, wherein the dying gasp alarm is transmitted to the OLT via atleast one of a Physical Layer Operations and Maintenance (PLOAM) messageand an Optical Network Termination Management and Control Interface(OMCI) message.
 12. The system of claim 8, wherein the power failurecomprises at least one of a power outage, a cut electrical cable, adefective power supply, and a dead or near dead backup battery.
 13. Thesystem of claim 8, wherein the notification is transmitted when a backupbattery reaches a given voltage.
 14. A computer-readable medium havinginstructions stored thereon for execution by a processor to perform amethod for notifying an optical line termination (OLT) of a powerfailure, the method comprising: receiving a notification of a powerfailure at an optical network termination (ONT); in response toreceiving the notification, receiving power from a dedicated powerstorage unit dedicated to providing power for transmitting a dying gaspalarm; and transmitting the dying gasp alarm to the OLT utilizing atleast a portion of the power from the dedicated power storage unit, thedying gasp alarm notifying the OLT of the power failure.
 15. Thecomputer-readable medium of claim 14, the method further comprising: inresponse to receiving the notification, terminating a power-consumingdevice or driver.
 16. The computer-readable medium of claim 14, whereinthe dedicated power storage unit comprises a capacitor.
 17. Thecomputer-readable medium of claim 14, wherein the dying gasp alarm istransmitted to the OLT via a Physical Layer Operations and Maintenance(PLOAM) message.
 18. The computer-readable medium of claim 14, whereinthe dying gasp alarm is transmitted to the OLT via an Optical NetworkTermination Management and Control Interface (OMCI) message.
 19. Thecomputer-readable medium of claim 14, wherein the power failurecomprises at least one of a power outage, a cut electrical cable, adefective power supply, and a dead or near dead backup battery.
 20. Thecomputer-readable medium of claim 14, wherein the notification istransmitted when a backup battery reaches a given voltage.